ANALYSIS OF HIGH-RESOLUTION MESOSPHERIC SODIUM TWILIGHT SPECTRAL EMISSION PROFILES

High-resolution Fabry-Perot spectrometers have been used for observati ons of mesospheric sodium spectral emissions excited by resonant scatt ering of sunlight. These observations are used to estimate winds and t emperatures in the emission region. Hollow-cathode lamps have been use d to define the rest wavelength for calculation of wind estimates from the Doppler shift of sky emission. Careful analysis of both lamp and sky spectra show the presence of self-absorption. The nature of the ab sorption is different for lamp and sky profiles, in the former case ab sorption occurs after emission, and in the latter absorption occurs in the incident radiation prior to emission. There is a further complica tion in the latter case, namely, the Doppler shift of the absorption i s determined by the wind component in the direction of the Sun while t he Doppler shift of the emission is determined by the wind component i n the direction of viewing. The effects of these absorption processes on wind and temperature estimates will be discussed.